Vol.22 No.5

Original Article

NEFA/nucleobindin-2 is a target autoantigen of the anti-Wa antibody and is associated with transfer RNA

Authors

Yoshitaka Imura1,2 , Yuichiro Shirai3 , Takaki Nojima1 , Ran Nakashima1 , Hajime Yamagata4 , Kiyomitsu Miyachi5 , Hajime Yoshifuji1 , Daisuke Kawabata1 , Koichiro Ohmura1 , Takashi Usui1 , Takao Fujii1 , Tsuneyo Mimori1

  • Department of Rheumatology and Clinical Immunology, Graduate School of Medicine, Kyoto University, 54 Shogoin-kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
  • Department of Rheumatology, Osaka Red Cross Hospital, Osaka, 543-8555, Japan
  • Division of Rheumatology, Department of Internal Medicine, Keio University School of Medicine, Shinjuku-ku, Tokyo, 160-8582, Japan
  • National Hospital Organization, Murayama Medical Center, Musashi-Murayama, Tokyo, 208-0011, Japan
  • Health Sciences Research Institute, Yokohama, Kanagawa, 240-0005, Japan
Received:

29 September 2011

Accepted:

12 December 2011

Published online:

24 January 2012

Full Text

PDF　(member's only)

Abstract

Objectives The anti-Wa antibody found in systemic sclerosis patients reacts with a transfer RNA (tRNA)-associated 48-kDa protein and immunoprecipitates several tRNAs. We investigated the Wa antigen and its binding to tRNA species.
Methods We performed molecular cloning of the Wa antigen and made its recombinant protein. To investigate Wa antigen distribution in the cell, we performed an indirect immunofluorescence study. To determine the Wabound tRNA species, we performed a reverse transcription (RT)-polymerase chain reaction (PCR) using the RNAs immunoprecipitated by anti-Wa antibody as templates, and synthetic primers of mammalian tRNA sequences. To clarify the tissue expression of Wa antigen, we performed quantitative and semi-quantitative PCR of the cDNA.
Results We demonstrated that the Wa antigen was identical to NEFA (DNA binding/EF-hand/acidic amino acid rich region), otherwise known as nucleobindin-2. A fulllength and an alternative splice variant cDNA lacking exon 11 were isolated by cloning NEFA cDNA. Anti-Wa-positive sera stained both the nucleus and cytoplasm of HEp-2 cells. RT-PCR suggested that Wa binds at least six tRNA species. In human tissues, NEFA is expressed predominantly in exocrine glands.
Conclusions We have demonstrated that the Wa antigen is NEFA or nucleobindin-2, which binds specific tRNA species, and is distributed in specific human tissues.

Key words

Anti-Wa antibody - NEFA/nucleobindin-2 - Splice variant - tRNA